OF THE ROCKS OV THE SOUTH OF IRELAND. 261 



Etheridge*. Both of these authors agree in considering the 

 Barnstaple, Pilton, and Baggy (or Marwood) beds as on the same 

 general geological horizon as the Carboniferous Slate and Coomhola 

 Grit, and. moreover, the Pickwell-Down Sandstone as the represen- 

 tative of the (Upper) Old Eed Sandstone of the South of Ireland. 

 For my own part, I think it is impossible to come to any other con- 

 clusion from a consideration both of their stratigraphical position, 

 their lithological constitution, and the organisms they respectively 

 contain. Considering the geographical distance between the south- 

 west of Cork, in which the Coomhola beds are most fully developed, 

 and North Devon, the general similarity on all these points is re- 

 markably striking, and the differences are only such as might be 

 expected to arise over tracts of similar extent at the present day. 



The points of greatest difference between the faunas of the two 

 areas seem to be, first, the occurrence of a few Upper Devonian 

 species peculiar to the Pilton beds, such as Phacojps latifrons, not 

 found in Ireland ; and, secondly, the occurrence of the lacustrine or 

 freshwater Anodonta Jiikesii, which has not yet been found in Devon- 

 shire, in the upper part of the Old Eed Sandstone in Ireland. 



(1) At the time when it was supposed that there was " an unbroken 

 sequence " from the Glengariff beds of the South of Ireland into the 

 Coomhola grit and Carboniferous Slate, and that the Glengariff beds 

 were the representatives of the Middle and Lower Devonian series f, 

 it was very difficult indeed, if not impossible, to account for many 

 of the palaeontological distinctions between the Upper Devonian beds 

 of North Devon and the Lower Carboniferous beds of the South of 

 Ireland ; but when it is known that (as I have endeavoured to prove 

 in the paper already referred to t) there is everywhere a great 

 hiatus between the Glengariff beds and the succeeding series, whether 

 Old Red or Carboniferous in Ireland, while there is a continuous 

 ascending series in Devonshire, the causes of these differences at 

 once become apparent. In Devonshire, many of the species belonging 

 to the (so-called) Upper Devonian (Pilton beds) come up from the 

 underlying Middle Devonian beds, having migrated for some distance 

 eastwards or southwards, and undergone modification of form during 

 the stage of the Pickwell-Down Sandstone, and then returned when 

 the conditions became favourable for their sustenance and vitality. 

 But no such ascent was possible in the Irish area, and all the species 

 (about 47 out of 56) which arc found in the Lower Carboniferous 

 beds of Ireland and in those of the " Upper Devonian " beds of 

 Devonshire were derived by migration from the Devonshire area. 

 The general conclusion from all this is that we must eliminate the 

 Marwood and Pilton beds from the Upper Devonian, and place them 

 in the Lower Carboniferous series. 



(2) The occurrence of Anodonta. Certain strata lying just below 

 the " CucuUcea-zone " and above the Pickwell-Down Sandstones, 

 similar in appearance, as well as in position, to the Kiltorcan beds of 

 the South of Ireland, may possibly yet be found to yield this re- 



* Supra cit. table xii. p. 698. t See Etheridge's table, loc. cif. 



\ Quart. Journ. Geol. Soc. vol. xxxv. p. 099. 



